The Laser Interferometer Gravitational-Wave Observatory, or LIGO, is a detector that detects gravitational waves by taking advantage of the way light interacts with both space and a propagating gravitational wave. Laser Interferometer Space Antenna, or LISA, is a triangular interferometer that will be launched in the next decade to discover gravitational waves sources. It will measure mass, spin and luminosity distance of a myriad of sources with unparalleled precision. The Global Astrometric Interferometer for Astrophysics, or GAIA, employs the use of telescopes, photometers, and a spectrometer. You might notice it does not use an interferometer! The interferometer technology was abandoned, but the name stuck. It will measure the positions of about a billion stars while creating a 3D map of the Galaxy with unprecedented accuracy.

Image credit: V. Altounian/Science

Image credit: LISA

Why is GAIA important?

GAIA will measure the luminosity distance to a gravitational wave source using stellar parallax. We will then compute GW chirp and then compare it with the total chirp, as measured by LISA, defining the astronomical chirp as the difference between the total chirp and the GW chirp. The results from this will give us some more insight on the internal astrophysics of mass transfar and tides in a binary! This is an example of multi-messenger astronomy, meaning that we can use multiple instruments to detect the same source in order to characterize and constrain the properties of the source system in ways that we would otherwise be unable to do with one instrument.

GAIA with the Milky Way in the background. Image credit: ESA

Multi-Messenger Astronomy flowchart for my summer 2016 project.

What are Gravitational Waves?

Gravitational waves are radiation that carry energy away from a system; the loss of energy causes the system to inspiral slowly over time. They squeeze and stretch space as they propagate through it! We need ultra-sensitive detectors because a GW's strength (and distortion of space) close the source is much stronger, but is much weaker by the time they travel hundreds of millions of light years to reach us.

Who Cares?

Measuring them allows us to make very precise distance measurements, which is often difficult to accomplish in astrophysics. Their emission from black hole binaries, neutron stars, white dwarf binaries, combined with GW detectors like LISA and LIGO allow us to detect black hole binaries that would otherwise be invisible to our telescopes.

This chart illustrates solar mass black holes (less then about 100 solar masses) with known masses. This includes six black holes detected by LIGO (the inspiraling black hole collisions create a new, third black hole), as well as the third GW candidate. Image credit: LIGO.

Here's an infographic on how GWs distort the fabric of space! Image credit: NASA.

More resources on gravitational waves:

  • Listen to what a GW sounds like
  • A breakdown of the two confirmed GW detections
  • Brian Greene explains gravitational waves and the LIGO detector on the late show

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    But First, What is a White Dwarf?

    A white dwarf is a stellar remnant of low to medium mass stars whose core is supported by pressure from electrons being so tightly compressed into small volumes, known as electron degeneracy pressure. With masses comparable to the sun stuffed inside volumes comparable to the earth they are extremely dense.

    An artistic rendition of a white dwarf. Image credit: All About Space/Imagine Publishing.

    Binaries

    My summer 2016 research was concerned with two white dwarfs orbiting one another, referred to as white dwarf binaries (WDBs).

    An artistic rendition of two white dwarf colliding into one another. Image credit: © Nature 2010.

    LISA is expected to be able to detect large numbers of WDBs and GAIA is expected to discover about 1,000 eclipsing binary systems composed of a WD and a main sequence star- a sizeable increase from 34, the currently known overall number of WDBs!