Category Archives: Astronomy

ESO: VLT captures first confirmed image of a planet forming

July 2, 2018 TopSpacer

A new report from ESO (European Southern Observatory):

First Confirmed Image of Newborn Planet Caught with ESO’s VLT
Spectrum reveals cloudy atmosphere

This spectacular image from the SPHERE instrument on ESO’s Very Large Telescope is the first clear image of a planet caught in the very act of formation around the dwarf star PDS 70. The planet stands clearly out, visible as a bright point to the right of the centre of the image, which is blacked out by the coronagraph mask used to block the blinding light of the central star. [Higher-res images]

SPHERE, a planet-hunting instrument on ESO’s Very Large Telescope, has captured the first confirmed image of a planet caught in the act of forming in the dusty disc surrounding a young star. The young planet is carving a path through the primordial disc of gas and dust around the very young star PDS 70. The data suggest that the planet’s atmosphere is cloudy.

Astronomers led by a group at the Max Planck Institute for Astronomy in Heidelberg, Germany have captured a spectacular snapshot of planetary formation around the young dwarf star PDS 70. By using the SPHERE instrument on ESO’s Very Large Telescope (VLT) — one of the most powerful planet-hunting instruments in existence — the international team has made the first robust detection of a young planet, named PDS 70b, cleaving a path through the planet-forming material surrounding the young star [1].

The SPHERE instrument also enabled the team to measure the brightness of the planet at different wavelengths, which allowed properties of its atmosphere to be deduced.

The planet stands out very clearly in the new observations, visible as a bright point to the right of the blackened centre of the image. It is located roughly three billion kilometres from the central star, roughly equivalent to the distance between Uranus and the Sun. The analysis shows that PDS 70b is a giant gas planet with a mass a few times that of Jupiter. The planet’s surface has a temperature of around 1000°C, making it much hotter than any planet in our own Solar System.

*This colourful image shows the sky around the faint orange dwarf star PDS 70 (in the middle of the image). The bright blue star to the right is χ Centauri. [Larger images]*

The dark region at the centre of the image is due to a coronagraph, a mask which blocks the blinding light of the central star and allows astronomers to detect its much fainter disc and planetary companion. Without this mask, the faint light from the planet would be utterly overwhelmed by the intense brightness of PDS 70.

“These discs around young stars are the birthplaces of planets, but so far only a handful of observations have detected hints of baby planets in them,” explains Miriam Keppler, who lead the team behind the discovery of PDS 70’s still-forming planet. “The problem is that until now, most of these planet candidates could just have been features in the disc.”

The discovery of PDS 70’s young companion is an exciting scientific result that has already merited further investigation. A second team, involving many of the same astronomers as the discovery team, including Keppler, has in the past months followed up the initial observations to investigate PDS 70’s fledgling planetary companion in more detail. They not only made the spectacularly clear image of the planet shown here, but were even able to obtain a spectrum of the planet. Analysis of this spectrum indicated that its atmosphere is cloudy.

PDS 70’s planetary companion has sculpted a transition disc — a protoplanetary disc with a giant “hole” in the centre. These inner gaps have been known about for decades and it has been speculated that they were produced by disc-planet interaction. Now we can see the planet for the first time.

“Keppler’s results give us a new window onto the complex and poorly-understood early stages of planetary evolution,” comments André Müller, leader of the second team to investigate the young planet. “We needed to observe a planet in a young star’s disc to really understand the processes behind planet formation.”

By determining the planet’s atmospheric and physical properties, the astronomers are able to test theoretical models of planet formation.

This glimpse of the dust-shrouded birth of a planet was only possible thanks to the impressive technological capabilities of ESO’s SPHERE instrument, which studies exoplanets and discs around nearby stars using a technique known as high-contrast imaging — a challenging feat. Even when blocking the light from a star with a coronagraph, SPHERE still has to use cleverly devised observing strategies and data processing techniques to filter out the signal of the faint planetary companions around bright young stars [2] at multiple wavelengths and epochs.

Thomas Henning, director at the Max Planck Institute for Astronomy and leader of the teams, summarises the scientific adventure:

“After more than a decade of enormous efforts to build this high-tech machine, now SPHERE enables us to reap the harvest with the discovery of baby planets!”

Notes
[1] The disc and planet images and the planet’s spectrum have been captured in the course of the two survey programmes called SHINE (SpHere INfrared survey for Exoplanets) and DISK (sphere survey for circumstellar DISK). SHINE aims to image 600 young nearby stars in the near-infrared using SPHERE’s high contrast and high angular resolution to discover and characterise new exoplanets and planetary systems. DISK explores known, young planetary systems and their circumstellar discs to study the initial conditions of planetary formation and the evolution of planetary architectures.

[2] In order to tease out the weak signal of the planet next to the bright star, astronomers use a sophisticated method that benefits from the Earth’s rotation. In this observing mode, SPHERE continuously takes images of the star over a period of several hours, while keeping the instrument as stable as possible. As a consequence, the planet appears to slowly rotate, changing its location on the image with respect to the stellar halo. Using elaborate numerical algorithms, the individual images are then combined in such a way that all parts of the image that appear not to move during the observation, such as the signal from the star itself, are filtered. This leaves only those that do apparently move — making the planet visible.

====

Astronomy

Videos: Night sky highlights for July 2018

July 1, 2018 TopSpacer

A preview of the night sky in July from NASA JPL: What’s Up for July 2018 – YouTube

And from the Hubble Space Telescope Institute:

=====

Asteroids & Comets, Astronomy, Space Science

Hubble: Interstellar visitor ‘Oumuamua leaving faster than expected

June 27, 2018 TopSpacer

The interstellar object that passed through the solar system continues to provide surprises:

Hubble sees `Oumuamua getting a boost
New results indicate interstellar nomad is a comet

`Oumuamua, the first interstellar object discovered in the Solar System, is moving away from the Sun faster than expected. This anomalous behaviour was detected using the NASA/ESA Hubble Space Telescope in cooperation with ground-based telescopes. The new results suggest that `Oumuamua is most likely a comet and not an asteroid. The discovery appears in the journal Nature.

This diagram shows the orbit of the interstellar object ‘Oumuamua as it passes through the Solar System. It shows the predicted path of ‘Oumuamua and the new course, taking the new measured velocity of the object into account. ‘Oumuamua passed the distance of Jupiter’s orbit in early May 2018 and will pass Saturn’s orbit January 2019. It will reach a distance corresponding to Uranus’ orbit in August 2020 and of Neptune in late June 2024. In late 2025 ‘Oumuamua will reach the outer edge of the Kuiper Belt, and then the heliopause — the edge of the Solar System — in November 2038.

`Oumuamua — the first interstellar object discovered within our Solar System — has been the subject of intense scrutiny since its discovery in October 2017 [1]. Now, by combining data from the NASA/ESA Hubble Space Telescope, the Canada-France-Hawaii Telescope, ESO’s Very Large Telescope and the Gemini South Telescope, an international team of astronomers has found that the object is moving faster than predicted. The measured gain in speed is tiny and `Oumuamua is still slowing down because of the pull of the Sun — just not as fast as predicted by celestial mechanics.

The team, led by Marco Micheli (European Space Agency) explored several scenarios to explain the faster-than-predicted speed of this peculiar interstellar visitor. The most likely explanation is that `Oumuamua is venting material from its surface due to solar heating — a behaviour known as outgassing [2]. The thrust from this ejected material is thought to provide the small but steady push that is sending `Oumuamua hurtling out of the Solar System faster than expected — as of 1 June, it is travelling with about 114 000 kilometres per hour.

Such outgassing is a typical behaviour for comets and contradicts the previous classification of `Oumuamua as an interstellar asteroid.

“We think this is a tiny, weird comet,” comments Marco Micheli. “We can see in the data that its boost is getting smaller the farther away it travels from the Sun, which is typical for comets.”

Usually, when comets are warmed by the Sun they eject dust and gas, which form a cloud of material — called a coma — around them, as well as the characteristic tail. However, the research team could not detect any visual evidence of outgassing.

“We did not see any dust, coma, or tail, which is unusual,” explains co-author Karen Meech (University of Hawaii, USA) who led the discovery team’s characterisation of `Oumuamua in 2017. “We think that ‘Oumuamua may vent unusually large, coarse dust grains.”

The team speculated that perhaps the small dust grains adorning the surface of most comets eroded during `Oumuamua’s journey through interstellar space, with only larger dust grains remaining. A cloud of these larger particles would not be bright enough to be detected by Hubble.

Not only is `Oumuamua’s hypothesised outgassing an unsolved mystery, but also its interstellar origin. The team originally performed the new observations on `Oumuamua to exactly determine its path which would have probably allowed it to trace the object back to its parent star system. The new results means it will be more challenging to obtain this information.

“The true nature of this enigmatic interstellar nomad may remain a mystery,” concludes team member Olivier Hainaut (European Southern Observatory, Germany). “`Oumuamua’s recently-detected gain in speed makes it more difficult to be able to trace the path it took from its extrasolar home star.”

This artist’s impression shows the first interstellar object discovered in the Solar System, `Oumuamua. Observations made with the NASA/ESA Hubble Space Telescope and others show that the object is moving faster than predicted while leaving the Solar System. Researchers assume that venting material from its surface due to solar heating is responsible for this behaviour. This outgassing can be seen in this artist’s impression as a subtle cloud being ejected from the side of the object facing the Sun. As outgassing is a behaviour typical for comets, the team thinks that `Oumuamua’s previous classification as an interstellar asteroid has to be corrected. [Higher res images]

Notes

[1]`Oumuamua, pronounced “oh-MOO-ah-MOO-ah”, was first discovered using the Pan-STARRS telescope at the Haleakala Observatory, Hawaii. Its name means “a messenger from afar, arriving first” in Hawaiian, and reflects its nature as the first known object of interstellar origin to have entered the Solar System.

[2] The team tested several hypotheses to explain the unexpected change in speed. They analysed whether solar radiation pressure, the Yarkovsky effect, or friction-like effects could explain the observations. It was also checked whether the gain in speed could have been caused by an impulse event (such as a collision), by `Oumuamua being a binary object or by `Oumuamua being a magnetised object. Also, the unlikely theory that `Oumuamua is an interstellar spaceship was rejected: the smooth and continuous change in speed is not typical for thrusters and the object is tumbling on all three axes, speaking against it being an artificial object.

Activism, Astronomy, SpaceCasts

Video: TMRO Orbit 11.25 – The evolution of galaxies with Dr. Charles Liu

June 25, 2018 TopSpacer

The latest episode of TMRO Space is now available on line: The evolution of galaxies with Dr. Charles Liu – Orbit 11.25 – TMRO

Dr. Charles Liu joins us to talk about the observable evolution of galaxies, quasar hunting and has some inspiring words about science communication.

Launch and news topics covered:

Launches:

Russia Launches GLONASS-M Satellite

Space News:

Einstein you genius

B-b-b-blackhole and the jets

The EU is taking down the trash

TMRO.tv is viewer supported:

TMRO shows are crowd funded. If you like this episode consider contributing to help us to continue to improve. Head over to http://www.patreon.com/tmro for funding levels, goals and all of our different rewards!

====

Astronomy

ESO: Hubble and VLT do most precise test yet of General Relativity at galactic scale

June 21, 2018 TopSpacer

A new report from ESO (European Southern Observatory):

VLT Makes Most Precise Test of Einstein’s General Relativity Outside Milky Way

An image of the nearby galaxy ESO 325-G004, created using data collected by the NASA/ESA Hubble Space Telescope and the MUSE instrument on the VLT. MUSE measured the velocity of stars in ESO 325-G004 to produce the velocity dispersion map that is overlaid on top of the Hubble Space Telescope image. Knowledge of the velocities of the stars allowed the astronomers to infer the mass of ESO 325-G004. The inset shows the Einstein ring resulting from the distortion of light from a more distant source by intervening lens ESO 325-004, which becomes visible after subtraction of the foreground lens light. > Larger images

Astronomers using the MUSE instrument on ESO’s Very Large Telescope in Chile, and the NASA/ESA Hubble Space Telescope, have made the most precise test yet of Einstein’s general theory of relativity outside the Milky Way. The nearby galaxy ESO 325-G004 acts as a strong gravitational lens, distorting light from a distant galaxy behind it to create an Einstein ring around its centre. By comparing the mass of ESO 325-G004 with the curvature of space around it, the astronomers found that gravity on these astronomical length-scales behaves as predicted by general relativity. This rules out some alternative theories of gravity.

Using the MUSE instrument on ESO’s VLT, a team led by Thomas Collett from the University of Portsmouth in the UK first calculated the mass of ESO 325-G004 by measuring the movement of stars within this nearby elliptical galaxy.

This schematic image represents how light from a distant galaxy is distorted by the gravitational effects of a nearer foreground galaxy, which acts like a lens and makes the distant source appear distorted, but brighter, forming characteristic rings of light, known as Einstein rings. An analysis of the distortion has revealed that some of the distant star-forming galaxies are as bright as 40 trillion Suns, and have been magnified by the gravitational lens by up to 22 times. > Larger images

Collett explains

“We used data from the Very Large Telescope in Chile to measure how fast the stars were moving in ESO 325-G004 — this allowed us to infer how much mass there must be in the galaxy to hold these stars in orbit.”

But the team was also able to measure another aspect of gravity. Using the NASA/ESA Hubble Space Telescope, they observed an Einstein ring resulting from light from a distant galaxy being distorted by the intervening ESO 325-G004. Observing the ring allowed the astronomers to measure how light, and therefore spacetime, is being distorted by the huge mass of ESO 325-G004.

Einstein’s general theory of relativity predicts that objects deform spacetime around them, causing any light that passes by to be deflected. This results in a phenomenon known as gravitational lensing. This effect is only noticeable for very massive objects. A few hundred strong gravitational lenses are known, but most are too distant to precisely measure their mass. However, the galaxy ESO 325-G004 is one of the closest lenses, at just 450 million light-years from Earth.

This infographic compares the two methods used to measure the mass of the galaxy ESO 325-G004. The first method used the Very Large Telescope to measure the velocities of stars in ESO 325-G004. The second method used the Hubble Space Telescope to observe an Einstein ring caused by light from a background galaxy being bent and distorted by ESO 325-G004. By comparing these two methods of measuring the strength of the gravity of ESO 325-G004, it was determined that Einstein’s general theory of relativity works on extragalactic scales — something that had not been previously tested. > Larger images

Collett continues

“We know the mass of the foreground galaxy from MUSE and we measured the amount of gravitational lensing we see from Hubble. We then compared these two ways to measure the strength of gravity — and the result was just what general relativity predicts, with an uncertainty of only 9 percent. This is the most precise test of general relativity outside the Milky Way to date. And this using just one galaxy!”

General relativity has been tested with exquisite accuracy on Solar System scales, and the motions of stars around the black hole at the centre of the Milky Way are under detailed study, but previously there had been no precise tests on larger astronomical scales. Testing the long range properties of gravity is vital to validate our current cosmological model.

These findings may have important implications for models of gravity alternative to general relativity. These alternative theories predict that the effects of gravity on the curvature of spacetime are “scale dependent”. This means that gravity should behave differently across astronomical length-scales from the way it behaves on the smaller scales of the Solar System. Collett and his team found that this is unlikely to be true unless these differences only occur on length scales larger than 6000 light-years.

“The Universe is an amazing place providing such lenses which we can use as our laboratories,” adds team member Bob Nichol, from the University of Portsmouth. “It is so satisfying to use the best telescopes in the world to challenge Einstein, only to find out how right he was.”