The difference between distance and dust

Measuring the distance to truly remote objects like galaxies, quasars and galaxy clusters is a crucial task in astrophysics, particularly when it comes to studying the early Universe, but it’s a difficult one. Only in the case of a few nearby objects like the Sun, planets and some nearby stars can we measure their distances directly. Beyond that, various indirect methods need to be used; one of the most important is by examining Type Ia supernovae, and this is where the NASA/ESA Hubble Space Telescope comes in.

NGC 3810, the galaxy featured in this image, was the host of a Type Ia supernova in 2022. In early 2023 Hubble focused on this and a number of other galaxies to closely examine recent Type Ia supernovae. This kind of supernova results from a white dwarf exploding, and they all have a very consistent brightness. That allows them to be used to measure distances: we know how bright a Type Ia supernova should be, so we can tell how far away it must be from how dim it appears. One uncertainty in this method is that intergalactic dust in between Earth and a supernova blocks some of its light. How do you know how much of the reduction in light is caused by distance, and how much by dust? With the help of Hubble, there’s a clever workaround: take images of the same Type Ia supernovae in ultraviolet light, which is almost completely blocked by dust, and in infrared light, which passes through dust almost unaffected. By carefully noting how much light comes through at each wavelength, the relationship between supernova brightness and distance can be calibrated to account for dust. Hubble can observe both these wavelengths of light in great detail with the same instrument. That makes it the perfect tool for this experiment, and indeed, some of the data used to make this beautiful image of NGC 3810 were focused on its 2022 supernova. You can see it as a point of light just below the galactic nucleus, or in the annotated image here.

There are many ways to measure cosmic distances; because Type Ia supernovae are so bright, they are one of the most useful and accurate tools, when they’re spotted. Many other methods must be used as well, either as an independent check against other distance measurements or to measure at much closer or farther distances. One such method that also works for galaxies is comparing their rotation speed to their brightness; based on that method, NGC 3810 is found to be 50 million light-years from Earth.

[Image Description: A spiral galaxy seen almost face-on. Large spiral arms whirl out from its centre, filling the scene. They glow faintly blue from the stars within, with some small bright patches of blue and pink marking areas of star formation. They are overlaid with thin filaments of dark reddish dust that block light. The galaxy’s centre shines brightly white.]

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Credit:

ESA/Hubble & NASA, D. Sand, R. J. Foley

About the Image

Id:potw2428a
Type:Observation
Release date:8 July 2024, 06:00
Size:3439 x 3097 px

About the Object

Name:NGC 3810
Distance:50 million light years
Constellation:Leo
Category:Galaxies

Image Formats

r.titleLarge JPEG
4.7 MB
r.titleScreensize JPEG
389.2 KB

Zoomable


Wallpapers

r.title1024x768
431.2 KB
r.title1280x1024
715.9 KB
r.title1600x1200
1.0 MB
r.title1920x1200
1.3 MB
r.title2048x1536
1.7 MB

Coordinates

Position (RA):11 40 58.75
Position (Dec):11° 28' 18.34"
Field of view:2.27 x 2.05 arcminutes
Orientation:North is 25.0° left of vertical


Colours & filters

BandWavelengthTelescope
Ultraviolet
UV
275 nm Hubble Space Telescope
WFC3
Ultraviolet
UV
300 nm Hubble Space Telescope
WFC3
Optical
U
336 nm Hubble Space Telescope
WFC3
Optical
V
555 nm Hubble Space Telescope
WFC3
Optical
I
814 nm Hubble Space Telescope
ACS
Infrared
J
1.25 μm Hubble Space Telescope
WFC3
Infrared
Y
1.05 μm Hubble Space Telescope
WFC3
Infrared
JH
1.4 μm Hubble Space Telescope
WFC3
Infrared
H
1.6 μm Hubble Space Telescope
WFC3

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