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Proxima Centauri To Bend Starlight For Planet Hunt 23

Posted by Unknown Lamer
from the londo-says-hi dept.
astroengine writes "In October 2014 and again February 2016 Proxima Centauri, the closest star system to our Solar System, will pass in front of two distant stars allowing astronomers a rare opportunity to use Einstein's General Relativity to potentially detect hidden exoplanets around the star system. As Proxima Centauri blocks the distant starlight from our perspective, the gravitational field will bend the distant light to create a microlensing event. The transient brightening can then be analyzed and the gravitational presence of any worlds may be revealed. The research, announced Monday at the American Astronomical Society meeting in Indianapolis, has been submitted for publication in the Astrophysical Journal."
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Proxima Centauri To Bend Starlight For Planet Hunt

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  • by Impy the Impiuos Imp (442658) on Monday June 03, 2013 @06:53PM (#43900625) Journal

    Why is it called "microlensing" anyway? The lens is bigger than everything all himans have done through all human history put together.

    It should be called humungiddy lensing.

    • If you ignore the "gravitational" bit and compare it to physical lenses. But it's being compared to using a galaxy or *galaxy cluster* as a lens. It's micro.
    • by Raenex (947668) on Monday June 03, 2013 @08:04PM (#43900995)

      "Why is it called "microlensing" anyway?"

      You got me curious, and I thought the Wikipedia article would have the answer, but instead I'm copying this from the talk page [wikipedia.org] on microlensing by somebody who claims to have worked as an astronomer:

      I've tried to fix the fuzzyness of the definition of microlensing with a new one: Microlensing is the subset of gravitational lensing whose variations in time can be measured. Typically, this means that the lens mass must be small enough that it will cross its own Einstein ring [wikipedia.org] radius in less than the time it takes for a graduate student to finish a PhD thesis. The EROS collaboration is analysing our own and MACHOs data for evidence of very long time scale events of order 100s or 1000s of years (see sec. 5.6 of [1] [arxiv.org]). Although these may not be confirmed as microlensing events (rather than some other very long time-scale variability), the non-detection of these events would allow a limit on dark matter by 100-1000 Mo MACHOs. Any event where the lens mass is so big and far away that it takes millions of years to cross its einstein ring radius, and thus changes too slowly in time to be studied in the time domain, is a "macrolens".

      I also disagree with the four definitions by MDAstronomer. It is not true that any lensing event with unresolved images is microlensing. A galaxy can lens a quasar, but have the images be too close to be resolved. This is not microlensing. Likewise,lensing by a compact object does not describe microlensing. "Any" gravitational lens must be physically smaller or about the same size as its own einstein radius to cause any measurable lensing effect. That is why we do not see any lensing effects from the Moon. It is so close that its Einstein radius is tiny. However, if the moon were a few kiloparsecs away, its einstein radius would be larger than its physical radius and it could be a perfectly ordinary microlens. The supermassive black hole at the center of the milky way is a compact object, but it cannot be a microlens... its einstein radius is too big for any changes in lensing to be monitored in time. It could in principle be a macrolens if there were a quasar right behind it. The microlensing at the edges of gravitationally lensed quasars is called microlensing because it causes time-varying effects in the apparent flux of the images. This has been significant because it interferes with attempts to use these gravitational lenses to measure the Hubble Constant.

      The time-varying nature of a microlens is the key to all of its observations. And the need to take over large blocks of telescope time to do microlensing has revolutionized time-domain astronomy in general, in part through a bureaucratic reorganization of Telescope Allocation Committees and the advent of dedicated telescopes. There have been great resulting changes not only in microlensing but in searches for supernovae, asteroids, variable stars.

      None of the various types of microlensing observations (photometric brightenning, astrometric shift, interferometric visibility reduction due to image splitting, shifts in color, spectrum, or variability amplitude) are strong enough to determine a microlensing event from a single observation. All of them require detecting some change in time, if only because there are plenty of natural causes that can mimic any one of the shifts for a single measurement. For example, how could one seperate a star which was split into two images from an ordinary binary star without time-domain information?

      I disagree with Mike's splitting of lensing into strong, weak and microlensing. A lens is strong if it is within one Einstein radius of the line of sight to the source, and weak otherwise. Nearly all photometric microlenses are strong lenses, but astrometric lensing is much more sensitive to weak lensing than photometric lensing. Ed

    • No fret. It is all explained here [phdcomics.com].

  • by Anonymous Coward

    Proxima Centauri, the closest star system to our Solar System

    Proxima centauri is a star in the Alpha Centauri star system.

    • by gatkinso (15975)

      From what I have read, it hasn't been fully determined that Proxima is gravitationally bound to the Alpha Centauri binary system.

      • Wiki [wikipedia.org] refs a paper that states:

        Ever since the discovery of Proxima it has been suspected to be a true companion of the Alpha Centauri binary star system. At a distance to Alpha Centauri of just 0.21 ly (15,000 ± 700 astronomical units [AU]),[15] Proxima Centauri may be in orbit around Alpha Centauri, with an orbital period of the order of 500,000 years or more. For this reason, Proxima is sometimes referred to as Alpha Centauri C. Modern estimates, taking into account the small separation between and r

        • by isorox (205688)

          the chance of the observed alignment being a coincidence is roughly [a million to one]

          But still they come?

  • Evan better idea... (Score:4, Interesting)

    by Genda (560240) <mariet@@@got...net> on Monday June 03, 2013 @08:11PM (#43901019) Journal

    One would think that with a good model of the gravitational light bending effect, it would be possible to convert Alpha Centauri into the objective lens of the largest telescope in history. Of course with a distance of 4+ ly, we may be well beyond the focal length of the star gravitational lens, In which case it might be a better microscope than a telescope.

    Of course you have to eclipse the star to remove its light, but it would still prove a fascinating experiment. Has anyone thought of using the Sun to image distant solar systems at its focal point (and does anyone here know if that's even inside the solar system?)

    • by Immerman (2627577)

      Short answer: yes. And the minimum distance to use our sun as a lens is something like 600-750 AU (I forget exactly). For reference Voyager 1 is currently at about 124 AU. So well outside our solar system by most definitions, though still near enough that it could orbit the sun easily enough, and in fact well within the orbits of the hypothetical Oort cloud objects.

      And in fact I imagine Alpha Centauri has been used as a lens every time something of interest has passed behind it since we discovered the gr

  • And still the ARM refuses to send help to Wunderland to help fight off the Kzin.

  • Proxima Centauri To Bend Starlight For Planet Hunt

    Now there's a beautiful piece of inspiring intersteller cooperation. Down here on Earth we can't even club together to go back to the Moon.

  • Micro-lensing has found the 3rd most number of planets after the doppler-shift and transit methods. #4 is direct imaging of "warm" planets in IR. Micro-lensing has the least bias toward large-close planets of the three methods.
  • The idea is to look for bightenings in the Kepler data rather than dimmings. Solar storms can masquerade as brightenings. But they may have a different shaped time history than lensing. And storms should occur more than once.

    I asked the Kepler Principal Investigator about micro-lensing in a talk she gave five years ago, but she dismissed it. But Ihave seen other news articles talk about this possibility. We could look for these ourselves by downloading Kepler data.

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