Hubble Observations Used to Measure Mass of Lone White Dwarf Star LAWD 37

Hubble Observations Used to Measure Mass of Lone White Dwarf Star LAWD 37

This graphic shows how microlensing was used to measure the mass of a white dwarf star.

The dwarf, called LAWD 37, is a burned-out star in the center of this Hubble Space Telescope image. Though its nuclear fusion furnace has shut down, trapped heat is sizzling on the surface at 180,000 degrees Fahrenheit, causing the stellar remnant to glow fiercely.

The inset box plots how the dwarf passed in front of a background star in 2019. The wavy blue line traces the dwarf's apparent motion across the sky as seen from Earth. Though the dwarf is following a straight trajectory, the motion of Earth orbiting the Sun imparts an apparent sinusoidal offset due to parallax. (The star is only 15 light-years away. Therefore, it is moving at a faster rate against the stellar background.)

As it passed by the fainter background star, the dwarf's gravitation field warped space (as Einstein's theory of general relativity predicted a century ago). And this deflection was precisely measured by Hubble's extraordinary resolution. The amount of deflection yields a mass for the white dwarf of 56 percent our Sun's mass and provides insights into theories of the structure and composition of white dwarfs. This is the first time astronomers directly measured the mass of a single, isolated white dwarf star, thanks to a "funhouse mirror" trick of nature.

Credits

Science

NASA, ESA, Peter McGill (UC Santa Cruz, IoA), Kailash Sahu (STScI)

Image Processing

Joseph DePasquale (STScI)

About The Object
Object Name LAWD 37 (LP 145-141)
Object Description Isolated White Dwarf
R.A. Position 11:45:42.9205
Dec. Position -64:50:29.459
Constellation Musca
Distance About 15 light-years
Dimensions Image is 1.2 arcmin across (about 0.005 light-years)
About The Data
Data Description This image was created with Hubble data from proposals: , , and (K. Sahu).
Instrument WFC3/UVIS
Exposure Dates 9 pointings between May 2019 and Sep 2020
Filters F555W, F814W
About The Image
Color Info These images are a composite of separate exposures acquired by the Hubble Space Telescope using the WFC3/UVIS instrument. Several filters were used to sample specific wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are:   Cyan: F555W, Orange: F814W
Compass Image A field of dark space scattered with numerous small points of light, with a relatively large and bright blue-white star in the center. The star has Hubble’s characteristic cross-shaped diffraction pattern. To the upper left, just within the blue-white glow of the star, is a much smaller white dot. To the upper right of the large star is a rectangular zoom-in showing the middle third of the large star, labeled “LAWD 37,” along with the smaller white circle labeled “background star.” The zoom-in also includes a curvy blue line that begins on the right near the middle of the large star LAWD 37 and ends near the lower left of the box. The curvy blue line is labeled “path of LAWD 37.” Along the path are nine small solid red squares marking the relative location of LAWD 37 with respect to the background star at nine different points in time. The squares are not evenly spaced along the line. There is a cluster just below the background star.
About The Object
Object Name A name or catalog number that astronomers use to identify an astronomical object.
Object Description The type of astronomical object.
R.A. Position Right ascension – analogous to longitude – is one component of an object's position.
Dec. Position Declination – analogous to latitude – is one component of an object's position.
Constellation One of 88 recognized regions of the celestial sphere in which the object appears.
Distance The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.
Dimensions The physical size of the object or the apparent angle it subtends on the sky.
About The Data
Data Description
  • Proposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
  • Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.
Instrument The science instrument used to produce the data.
Exposure Dates The date(s) that the telescope made its observations and the total exposure time.
Filters The camera filters that were used in the science observations.
About The Image
Image Credit The primary individuals and institutions responsible for the content.
Publication Date The date and time the release content became public.
Color Info A brief description of the methods used to convert telescope data into the color image being presented.
Orientation The rotation of the image on the sky with respect to the north pole of the celestial sphere.

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