---
title: "Backyard Worlds"
chunk: 2/3
source: "https://en.wikipedia.org/wiki/Backyard_Worlds"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:13:25.266684+00:00"
instance: "kb-cron"
---

In October 2018, a participant in the project discovered LSPM J0207+3331 – the oldest and coldest white dwarf known to host a circumstellar disk, despite being 3 billion years old. The time since this star became a white dwarf is far longer than the expected timescale for such disks to be cleared from a system. The disk consists of two rings at different temperatures. This star has been studied with the Keck telescope and is the subject of ongoing research.

=== W2150AB ===

At the 235th meeting of the American Astronomical Society in January 2020 the discovery of the wide brown dwarf binary W2150AB was presented by Jacqueline Faherty. The L1+T8 co-moving system is separated by 341 au, being one of three brown dwarf binary systems where both objects are easily resolved by ground-based telescopes. The system has the lowest gravitational binding energy for a brown dwarf binary that is not young and with the primary being a L-dwarf or later.

=== WISE J0830+2837 ===

The discovery of WISE J0830+2837, the first Y-dwarf discovered by volunteers was also presented at the 235th meeting by project scientist Daniella Bardalez Gagliuffi. The Y-dwarf was not detected by the Hubble Space Telescope, but the Spitzer Space Telescope did detect this object due to it observing at longer wavelengths of light. It is about 11.2 parsec (36.5 light years) distant and has a temperature of about 350 K (77 °C or 170 °F).  This estimated temperature would place it between the majority of the Y-dwarf population so far identified and WISE 0855−0714, the coldest object of this type known.

=== T subdwarfs ===
A paper was published in the Astrophysical Journal in July 2020 reporting the discovery of two unusual brown dwarfs; WISEA J041451.67-585456.7 was discovered by Backyard Worlds volunteers and WISEA J181006.18-101000.5 by the NEOWISE Proper Motion Survey, also with the aid of a Backyard Worlds citizen scientist. These high-proper motion objects display unique colors and near-infrared spectra that do not fully match current models. The models producing the best matches to the spectra imply the brown dwarfs have [Fe/H] ≤ -1, meaning they have extremely sub-solar metallicity, containing far lower amounts of elements heavier than hydrogen or helium compared to the Sun. The estimates from the model spectra suggest that these objects have up to 30 times less iron than typical for known brown dwarfs. The authors argue that the spectral properties combined with the estimated low temperatures of approximately 1200-1400 K make these brown dwarfs likely the first extreme subdwarfs of the T spectral class (esdTs) to be identified.  The extremely low metallicity implies these brown dwarfs are very old, approximately 10 billion years, as the galaxy at this time would have featured lower quantities of heavy elements. This provides evidence that substellar objects were able to form in the low metallicity environment of the Milky Way's past.
A study by Lodieu et al. observed WISE1810 with a range of ground-based telescopes, using imaging and spectroscopy. They find a closer distance of 8.9+0.7−0.6 parsec, a radius of 0.67+0.32−0.20 RJ and a mass of 17+56−12 MJ. This makes WISE1810 the closest extreme ultra-cool subdwarf and the closest extreme metal-poor brown dwarf known to science, as of June 2022. The optical and infrared spectrum does not show any methane or carbon monoxide absorption, which is expected at these temperatures of about 800 K, and the WISE photometry suggest a depleted methane atmosphere. Only H2 CIA and water vapor absorption is detected, suggesting a carbon-deficient and metal-poor atmosphere, or alternatively an oxygen-enhanced atmosphere.
A study in 2024 discovered three additional T-type subdwarfs and introduced a new classification system for T subdwarfs. This system classified WISE 1810 as a esdT3: and WISE 0414 as a esdT6:. The study also found L and T dwarfs with unusual galactic orbits. 2MASS J053253.46+824646.5 (previous known L subdwarf) and CWISE J113010.07+313944.7 (mild T-subdwarf) were identified as possible members of the Thamnos stellar streams. These two brown dwarfs are on a retrograde Galactic orbit. CWISE J155349.96+693355.2 was found to be a possible member of the Helmi stream (prograde galactic orbit). Three T dwarfs (SDSS J014016.89+015054.1, CWISEP J111055.12-174738.2, and CWISEP J145837.91+173450.1) are found to have high metallicity and might be part of the high velocity thick disk. This population originates from the inner Milky Way and was scattered outwards.

=== 95 cold brown dwarfs observed with Spitzer ===

In August 2020, the Backyard Worlds team published a paper in the Astrophysical Journal detailing follow-up conducted using the Spitzer Space Telescope on a sample of the coldest discoveries that had been made before the telescope was decommissioned. 95 had Spitzer mid-infrared colors consistent with being a cold brown dwarf, with 75 of these having their proper motion confirmed by comparison to their position in WISE images.  Among the discoveries highlighted as most significant were; 3 possible T subdwarfs based on high tangential velocity estimates, a rare widely separated T8 companion to the white dwarf LSPM J0055+5948, and 5 new Y dwarfs, four of which (including the previously published WISE J0830+2837) where Spitzer colors indicate they have spectral types Y1 or later, with only at most 6 of these coldest set of brown dwarfs previously being known. The T8 companion to the white dwarf LSPM J0055+5948 could be the oldest (7-13 billion years old) brown dwarf known to science, together with Wolf 1130C (>10 billion years old).