Here is NASA JPL’s report on what to look for in the sky in the coming month:
The Hubble Space Telescope organization provides another preview of the May night sky:
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Category Archives: Astronomy
Hubble sees first gravitationally lensed “standard candle” supernova
A galaxy or other massive object can bend light. Light from a star far beyond and behind such an object from our point of view can be bent just like light going through a lens. This lens effect can result in multiple views of the same star. This gravitational lens phenomena has been studied for many years but no one till now has used it to see a special kind of “standard candle” supernova that provides a way to measure distances in the universe. Here is a report on these new observations with the Hubble space telescope:
Hubble observes first multiple images of explosive distance indicator
A Swedish-led team of astronomers used the NASA/ESA Hubble Space Telescope to analyse the multiple images of a gravitationally lensed type Ia supernova for the first time. The four images of the exploding star will be used to measure the expansion of the Universe. This can be done without any theoretical assumptions about the cosmological model, giving further clues about how fast the Universe is really expanding. The results are published in the journal Science.
This animation shows the phenomenon of strong gravitational lensing. This effect caused the supernova iPTF16geu to appear 50 times brighter than under normal circumstances and to be visible on the sky four times. Credit: ESA/Hubble, L. Calçada
Type Ia supernovae always have the same intrinsic brightness, so by measuring how bright they appear astronomers can determine how far away they are. They are therefore known as standard candles. These supernovae have been used for decades to measure distances across the Universe, and were also used to discover its accelerated expansion and infer the existence of dark energy. Now the supernova iPTF16geu allows scientists to explore new territory, testing the theories of the warping of spacetime on smaller extragalactic scales than ever before.
“Resolving, for the first time, multiple images of a strongly lensed standard candle supernova is a major breakthrough. We can measure the light-focusing power of gravity more accurately than ever before, and probe physical scales that may have seemed out of reach until now,” says Ariel Goobar, Professor at the Oskar Klein Centre at Stockholm University and lead author of the study.
The critical importance of the object meant that the team instigated follow-up observations of the supernova less than two months after its discovery. This involved some of the world’s leading telescopes in addition to Hubble: the Keck telescope on Mauna Kea, Hawaii, and ESO’s Very Large Telescope in Chile. Using the data gathered, the team calculated the magnification power of the lens to be a factor of 52. Because of the standard candle nature of iPTF16geu, this is the first time this measurement could be made without any prior assumptions about the form of the lens or cosmological parameters.
Last month saw the inauguration of a new Hubble observing program: Frontier Fields. This will use the powerful magnifying properties of massive galaxy clusters to peer even deeper into the space around us. Hubblecast 70 takes a look at this phenomenon — known as gravitational lensing — exploring how it works, and how it can help us to uncover the secrets of the very distant Universe.
Currently the team is in the process of accurately measuring how long it took for the light to reach us from each of the four images of the supernova. The differences in the times of arrival can then be used to calculate the Hubble constant — the expansion rate of the Universe — with high precision [4]. This is particularly crucial in light of the recent discrepancy between the measurements of its value in the local and the early Universe (heic1702).
“The discovery of iPTF16geu is truly like finding a somewhat weird needle in a haystack,” remarks Rahman Amanullah, co-author and research scientist at Stockholm University. “It reveals to us a bit more about the Universe, but mostly triggers a wealth of new scientific questions.”
Studying more similarly lensed supernovae will help shape our understanding of just how fast the Universe is expanding. The chances of finding such supernovae will improve with the installation of new survey telescopes in the near future.
Notes
[1] iPTF16geu was initially observed by the iPTF (intermediate Palomar Transient Factory) collaboration with the Palomar Observatory. This is a fully automated, wide-field survey delivering a systematic exploration of the optical transient sky.
[2] This corresponds to a redshift of 0.4. The lensing galaxy has a redshift of 0.2.
[3] Gravitational lensing is a phenomenon that was first predicted by Albert Einstein in 1912. It occurs when a massive object lying between a distant light source and the observer bends and magnifies the light from the source behind it. This allows astronomers to see objects that would otherwise be to faint to see.
[4] For each image of the supernova, the light is not bent in the same way. This results in slightly different travel times. The maximum time delay between the four images is predicted to be less than 35 hours.
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ESO: New exoplanet is good candidate in search for signs of life
The latest report from ESO (European Southern Observatory):
Newly Discovered Exoplanet May be Best Candidate
in Search for Signs of Life
An exoplanet orbiting a red dwarf star 40 light-years from Earth may be the new holder of the title “best place to look for signs of life beyond the Solar System”. Using ESO’s HARPS instrument at La Silla, and other telescopes around the world, an international team of astronomers discovered a “super-Earth” orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth and has likely retained most of its atmosphere. This, along with the fact that it passes in front of its parent stars as it orbits, makes it one of the most exciting future targets for atmospheric studies. The results will appear in the 20 April 2017 issue of the journal Nature.
“This is the most exciting exoplanet I’ve seen in the past decade,” said lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics (Cambridge, USA). “We could hardly hope for a better target to perform one of the biggest quests in science — searching for evidence of life beyond Earth.”
“The present conditions of the red dwarf are particularly favourable — LHS 1140 spins more slowly and emits less high-energy radiation than other similar low-mass stars,” explains team member Nicola Astudillo-Defru from Geneva Observatory, Switzerland [2].
For life as we know it to exist, a planet must have liquid surface water and retain an atmosphere. When red dwarf stars are young, they are known to emit radiation that can be damaging for the atmospheres of the planets that orbit them. In this case, the planet’s large size means that a magma ocean could have existed on its surface for millions of years. This seething ocean of lava could feed steam into the atmosphere long after the star has calmed to its current, steady glow, replenishing the planet with water.
This artist’s impression video shows an imaginary trip to the exoplanet LHS 1140b, which orbits a red dwarf star 40 light-years from Earth and may be the new holder of the title “best place to look for signs of life beyond the Solar System”. Using ESO’s HARPS instrument at La Silla, and other telescopes around the world, an international team of astronomers discovered this super-Earth orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth and has likely retained most of its atmosphere. Credit: ESO/spaceengine.org
The discovery was initially made with the MEarth facility, which detected the first telltale, characteristic dips in light as the exoplanet passed in front of the star. ESO’s HARPS instrument, the High Accuracy Radial velocity Planet Searcher, then made crucial follow-up observations which confirmed the presence of the super-Earth. HARPS also helped pin down the orbital period and allowed the exoplanet’s mass and density to be deduced [3].
This super-Earth may be the best candidate yet for future observations to study and characterise its atmosphere, if one exists. Two of the European members of the team, Xavier Delfosse and Xavier Bonfils both at the CNRS and IPAG in Grenoble, France, conclude:
“The LHS 1140 system might prove to be an even more important target for the future characterisation of planets in the habitable zone than Proxima b or TRAPPIST-1. This has been a remarkable year for exoplanet discoveries!” [4,5].
In particular, observations coming up soon with the NASA/ESA Hubble Space Telescope will be able to assess exactly how much high-energy radiation is showered upon LHS 1140b, so that its capacity to support life can be further constrained.
Further into the future — when new telescopes like ESO’s Extremely Large Telescope are operating — it is likely that we will be able to make detailed observations of the atmospheres of exoplanets, and LHS 1140b is an exceptional candidate for such studies.
[1] The habitable zone is defined by the range of orbits around a star, for which a planet possesses the appropriate temperature needed for liquid water to exist on the planet’s surface.
[2] Although the planet is located in the zone in which life as we know it could potentially exist, it probably did not enter this region until approximately forty million years after the formation of the red dwarf star. During this phase, the exoplanet would have been subjected to the active and volatile past of its host star. A young red dwarf can easily strip away the water from the atmosphere of a planet forming within its vicinity, leading to a runaway greenhouse effect similar to that on Venus.
[3] This effort enabled other transit events to be detected by MEarth so that the astronomers could nail down the detection of the exoplanet once and for all.
[4] The planet around Proxima Centauri (eso1629) is much closer to Earth, but it probably does not transit its star, making it very difficult to determine whether it holds an atmosphere.
[5] Unlike the TRAPPIST-1 system (eso1706), no other exoplanets around LHS 1140 have been found. Multi-planet systems are thought to be common around red dwarfs, so it is possible that additional exoplanets have gone undetected so far because they are too small.
Australian citizen scientists spot four exoplanets in Kepler data
The Australian TV program ABC Stargazing Live with Brian Cox recently challenged its viewers to become citizen exoplanet finders. They succeeded within a couple of days in finding four “Super Earth” planets each about twice the size of earth.
- Exoplanet discovery by an amateur astronomer shows the power of citizen science – The Conversation
- Stargazing Live viewers find four-planet solar system via crowd-sourcing project – ABC News (Australian Broadcasting Corp.)
The discoveries were made using data from the Kepler space observatory available on the Exoplanet Explorers site, which is hosted by the Zooniverse citizen science organization.
Kepler observes thousands of stars and records the stars’ brightness for long continuous periods. If a star’s planet comes between the line of sight with the earth, a dip in the star’s brightness can be seen in the data.
The width and depth of the drop in the light and the frequency of the dips provides clues to the size of the planet and its orbital period and distance from its star.
While the above diagrams are very clean and unambiguous, most real data is noisy and messy. Human’s are still much better than computer algorithms in spotting structures and unexpected features in such data and that is why citizen science volunteers can provide very useful services for the pro scientists who are collecting the data, especially when there are huge amounts of such data.
In this case, the dips of four planets were seen in the light output of a star in the Aquarius constellation 600 light years from earth. This video provides more details about these exoplanets:
https://youtu.be/ZrFST9cvdAU
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MPIA: Atmosphere detected around exoplanet 1.4 diameter of earth
An announcement from the Max Planck Institute for Astronomy:
Atmosphere around low-mass Super-Earth detected
Astronomers have detected an atmosphere around the super-Earth GJ 1132b. This marks the first detection of an atmosphere around a low-mass Super-Earth, in terms of radius and mass the most Earth-like planet around which an atmosphere has yet been detected. Thus, this is a significant step on the path towards the detection of life on an exoplanet. The team, which includes researchers from the Max Planck Institute for Astronomy, used the 2.2 m ESO/MPG telescope in Chile to take images of the planet’s host star GJ 1132, and measuring the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while passing directly in front of their host star.
Astronomers’ current strategy for finding life on another planet is to detect the chemical composition of that planet’s atmosphere, on the look-out for certain chemical imbalances that require the presence of living organisms as an explanation. In the case of our own Earth, the presence of large amounts of oxygen is such a trace.
We’re still a long way from that detection though. Until the work described in this article, the (few!) observations of light from exoplanet atmospheres all involved planets much more massive than Earth: gas giants – relatives of our own Solar System’s Jupiter – and a large super-Earth with more than eight times the Earth’s mass. With the present observation, we’ve taken the first tentative steps into analyzing the atmosphere of smaller, lower-mass planets that are much more Earth-like in size and mass.
The planet in question, GJ 1132b, orbits the red dwarf star GJ 1132 in the Southern constellation Vela, at a distance of 39 light-years from us. Recently, the system has come under scrutiny by a team led by John Southworth (Keele University, UK). The project was conceived, and the observations coordinated, by Luigi Mancini, formerly of the Max Planck Institute for Astronomy (MPIA) and now working at the University of Rome Tor Vergata. Additional MPIA team members were Paul Mollière, and Thomas Henning.
The team used the GROND imager at the 2.2 m ESO/MPG telescope of the European Southern Observatory in Chile to observe the planet simultaneously in seven different wavelength bands. GJ 1132b is a transiting planet: From the perspective of an observer on Earth, it passes directly in front of its star every 1.6 days, blocking some of the star’s light.
The size of stars like GJ 1132 is well known from stellar models. From the fraction of starlight blocked by the planet, astronomers can deduce the planet’s size – in this case around 1.4 times the size of the Earth. Crucially, the new observations showed the planet to be larger one of the infrared wavelengths than at the others. This suggests the presence of an atmosphere that is opaque to this specific infrared light (making the planet appear larger), but transparent at all the others. Different possible versions of the atmosphere were then simulated by team members at the University of Cambridge and the Max Planck Institute for Astronomy. According to those models, an atmosphere rich in water and methane would explain the observations very well.
The discovery comes with the usual exoplanet caveats: while somewhat larger than Earth, and with 1.6 times Earth’s mass (as determined by earlier measurements), observations to date do not provide sufficient data to decide how similar or dissimilar GJ 1132b is to Earth. Possibilities include a “water world” with an atmosphere of hot steam.
The presence of the atmosphere is a reason for cautious optimism. M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets’ atmospheres. GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.
In any case, the new observations make GJ 1132b a high-priority target for further study by instruments such as the Hubble Space Telescope, ESO’s Very Large Telescope, and the James Webb Space Telescope slated for launch in 2018.
Background information
The team members are John Southworth (Keele University), Luigi Mancini (Max Planck Institute for Astronomy [MPIA], Universita die Roma Tor Vergata, INAF – Osservatorio Astrofisico di Torinio), Nikku Madhusudhan (University of Cambridge), Paul Mollière (MPIA), Simona Ciceri (Stockholm University), and Thomas Henning (MPIA).
The work described here has been published as J. Southworth et al., “Detection of the atmosphere of the 1.6 Earth mass exoplanet GJ 1132B” in the Astronomical Journal.